With reference to recent questions about overclocking (ie. What are the overclocking capabilities? ), is it possible to immersively cool the Raspi?
Presumably such a system would have to rely on finding a coolant that is non-toxic, non-conducting, and cheap.
There's also the physics of boiling - although a boiling coolant would be most effective, it would need a more sophisticated level of containment to avoid vapour escape.